This invention relates to a plug for a tap hole, and more specifically, to an expandable tap hole plug for use with metallurgical vessels.
Tap hole plugs are used to seal the tap hole of a metallurgical vessel while the vessel is in use. Because the size of such tap holes vary from vessel to vessel and widen with use, it is important that the tap hole plug be adjustable. Further, it is advantageous that such a tap hole plug have a contracted position in which it can easily be inserted within and withdrawn from a tap hole, and an expanded condition in which it securely plugs the tap hole.
U.S. Pat. No. 3,398,945 to Walpole, issued Aug. 27, 1968, shows a conical plug of a porous material that is inserted within an orifice to be plugged. The porosity of the plug allows molten metal to flow into the plug. When the metal cools, it solidifies to block the further flow of metal through the plug. It would be preferred to avoid using the metal that is being stored until required for collection for the plug. Furthermore, the hot atmosphere in the vicinity of the container makes it highly unlikely that the metal can cool to a temperature at which it solidifies and remain solidified until the orifice is unplugged.
U.S. Pat. No. 3,540,627 to Armstead, issued Nov. 17, 1970, uses a conical plug, a resilient refractory fiber pad for the plug and a mat of relatively inexpensive glass fiber interposed between the plug and the pad to provide economical backing for the pad. The plug is a solid, rigid member of fixed configuration that is movable axially to compress the resilient refractory fiber pad and its glass fiber backing against the wall of an orifice to be plugged. In one embodiment, the solid, rigid plug is made hollow to enable cooling air to be furnished about a line of contact between the plug and orifice.
U.S. Pat. No. 4,471,950 to La Bate, issued Sept. 18, 1984, shows a stopper plug formed of refractory materials, fibrous substances and consumable materials in a hollow conical plug that is expandable in a tap hole by movement of a rigid wedge-shaped member therein. The expanded stopper plug is capable of effectively sealing the tap hole for a predetermined time. In case of a slow market for the metal, it may become necessary to store the molten metal for more than said predetermined time.
One type of currently available expandable tap hole plug involves a conically shaped plug having a circular disc movable toward and away from the nose of the plug on a rod. Once the plug is inserted within a tap hole, the disc is moved until it causes the plug to expand to the point where the plug is tightly lodged within the tap hole. Once concern associated with use of such tap hole plugs is that the sidewall of the plug can buckle as the disc is moved relative to the plug. Further, because the point on the plug that is in contact with the inner wall of the tap hole is not necessarily, and most likely is not, the same point wherein the disc contacts the inner surface of the sidewall of the plug when the plug is in its expanded position, the seal between the plug and the tap hole is not as tight as it might be.
It is desired to improve upon the quality of the seal between the tap hole and the plug and to reduce the propensity of the sidewall of the plug to buckle when in its expanded position.